textproduct: Albany

WHAT HAS CHANGED

Slight Risk (Level 2 of 4)for Excessive Rainfall is in place across parts of northern Herkimer and northern Hamilton Counties through tonight, with a Marginal Risk (Level 1 of 4) across the remainder of the area.

Slight Risk for Excessive Rainfall has been nudged slightly northward to include the southern Berkshires for Monday. The Slight Risk now includes parts of Ulster, Dutchess, Berkshire and Litchfield Counties. A narrow area of Marginal Risk remains for areas to the north and northwest for Monday.

Marginal Risk (Level 1 of 5) for Severe Thunderstorms continues across much of the region (outside of the Adirondacks and Mohawk Valley) for Monday. Damaging winds continue to be the main threat with any isolated thunderstorms on Monday.

KEY MESSAGES

1) A slow moving cold front will result in periods of showers and thunderstorms across the entire region tonight into Monday. Heavy rainfall rates can result in isolated to scattered flash flooding, with areas that saw high rainfall amounts recently most susceptible to renewed flooding.

2) There is a marginal risk (level 1 of 5) for severe thunderstorms tomorrow afternoon for much of eastern NY and western New England, except the southwest Adirondacks and Mohawk Valley, with damaging winds the primary hazard.

DISCUSSION

KEY MESSAGE 1...

A frontal boundary is draped across the eastern Great Lakes and is nearly stationary at this time. However, this boundary will start shifting eastward for tonight into Monday, as an upper level disturbance over the Great Lakes moves eastward into the Northeast.

Ahead of the boundary, our area is within a rather moist and humid environment. Surface dewpoints have been surging up with values in the mid to upper 60s. The PWAT value on this morning's 12z KALY sounding was 1.61" but PWAT values are expected to rise, with many sources of guidance showing values to exceed 2.00" inches in valley areas by late tonight, which is about 2-3 STD above normal. Model soundings suggest that any precipitation will be highly efficient thanks to the combination of high PWATs, a narrow skinny CAPE profile and high freezing levels.

Some showers have already been spreading into western and northern areas this afternoon, but any precip so far today as been light. The best forcing is still off to the west, but this will be getting closer for tonight into early Monday. As this occurs, rounds of showers and expected for the overnight and into Monday morning. CAMs suggest the main window for heavy showers looks to be about midnight through daybreak, although another line could develop just ahead of the cold front for the late morning through early afternoon hours on Monday as well for southeastern areas. Although overall the precip should be progressive, there is the potential for some training of precip and areas to see repeated periods of showers and possible thunderstorms. CAMs suggests the highest totals may be across far northwestern areas for later today (western Adirondacks), as well as across southern areas, including the Catskills, mid Hudson Valley, NW CT and the Berkshires for late tonight into Monday. These are the areas favored for the potential for isolated to scattered flash flooding, as high rainfall rates may lead to flooding, especially within urban and poor drainage areas. Any areas that saw high rainfall last week continue to have high flows and wet soils, so these areas are also at risk for renewed flooding if any repeated rounds of rainfall occur. Overall, flooding appears to be mainly isolated to scattered in coverage and will likely not be as extreme or extensive as to what occurred last week.

Precip will wind down on Monday afternoon as the front crosses from west to east. With a drier westerly flow in place behind the front, dewpoints will be lowering for late Monday into Monday night.

KEY MESSAGE 2...

Just ahead of the cold front, a line of showers and thunderstorms is expected to develop across southeastern areas on Monday during the late morning to early afternoon hours. There looks to be sufficient shear to support some strong to severe thunderstorms, with 0-6 km bulk shear in the 35-40 kt range. If enough breaks of sun occur behind the morning steadier rainfall and the approaching cold front, there should be about 1000-2000 J/kg of SBCAPE in valley areas. This should allow for the risk for a few storms to produce wind damage. SPC has a Marginal Risk (Level 1 of 5) for much of the area outside of the Adirondacks and Mohawk Valley for Monday.

AVIATION /00Z MONDAY THROUGH FRIDAY/

Through 00Z Tue...VFR conditions begin the TAF cycle with mid level clouds 8-15 kft AGL over the TAF sites. However, some light showers are moving into KALB-KGFL with a prefrontal disturbance ahead of a cold front. An area of showers and potentially a few embedded thunderstorms will expand in coverage ahead of the front between 03Z-06Z/Mon with cigs/vsbys lowering into the MVFR range at all the TAF sites. The rainfall will become moderate to locally heavy in intensity between 06Z-12Z/Mon with low MVFR/IFR conditions. TEMPO groups were used for the IFR vsbys/cigs. IFR cigs/vsbys may persist at KGFL/KPOU/KPSF until 12Z-14Z/Mon before some improvement. We kept KALB MVFR during the morning. A lull in the pcpn will occur in the late morning into the early pm, and flight conditions may improve to VFR levels for cigs/vsbys with cloud bases 3.5-5 kft AGL or higher. However, a line of showers and thunderstorms will potentially form ahead of the cold front. We used PROB30 groups to bring the line through between 17Z-21Z/MON from KGFL/KALB to KPSF/KPOU where flight conditions may briefly drop to MVFR or even IFR conditions.

Southeast to south winds will be generally 5-10 KT tonight with a few gusts 15-20 KT at KALB/KPSF. The winds will veer to the south to southwest in the late morning into the afternoon at 5-10 KT and then shift to the west to northwest in the wake of the front in the mid to late pm at 10-15 KT with some gusts 20-25 KT. Strong wind gusts variable in direction at 30-35 KT may occur with any thunderstorms.

Outlook...

Mon Night to Tue Night: No Operational Impact. NO SIG WX. Wednesday: Low Operational Impact. NO SIG WX. Wednesday Night: Low Operational Impact. Slight Chance of SHRA. Thursday: High Operational Impact. Likely SHRA...TSRA. Thursday Night: Moderate Operational Impact. Chance of SHRA...TSRA. Friday: Moderate Operational Impact. Chance of SHRA...TSRA.

ALY WATCHES/WARNINGS/ADVISORIES

CT...None. NY...None. MA...None. VT...None.